000
FXUS63 KDLH 092120
AFDDLH
Area Forecast Discussion
National Weather Service Duluth MN
320 PM CST Fri Dec 9 2016
.SHORT TERM...(This evening through Saturday)
Issued at 320 PM CST Fri Dec 9 2016
High pressure builds into the northern Plains and upper Midwest into
Saturday resulting in colder temperatures but at least the
possibility for partly sunny skies in some locations on Saturday.
On the synoptic scale northwest to west-northwest flow continues
through the column. A mid-level shortwave trough will cross the
international border into central Lake Superior tonight which could
enhance the snow showers overnight tonight, but a strong high
pressure building in over the northern Plains will likely put an end
to the persistent snow shower activity by Saturday morning. Along
with the high pressure will come the coldest air of the season so
far with temperatures falling to below zero across much of the
Northland, with wind chill values approaching 10 to 20 below. The
high pressure will be centered over northern Minnesota by Saturday
afternoon, which could lead to some clearing skies as temperatures
struggle to reach the double digits - though on the bright side, at
least the highs will be positive! These highs will be 10-15 degrees
below normal, which will be the coldest highs *relative to normal*
since mid-summer. (Current Duluth forecast is 9 at the airport,
normal is 24 which would be 15 degrees below normal. You have to go
back to July 14 to find a high temp departure from normal more than
10 degrees, and if our forecast is perfect you need to go as far
back as a mid-May cold snap to find highs that were 15 degrees below
normal or greater.)
Cancelled the lake effect snow advisory and warning earlier today,
though the west-northwest winds may lead to a localized area of 1"+
tonight along the south shore between Maple and Sand Bay, but as the
high pressure builds in this activity should gradually cease.
Otherwise mostly cloudy overnight with occasional isolated snow
showers/flurries. Saturday should see a few peaks of sun as the mid
and high level clouds exit. Stratus layer will remain, but should be
thin enough to cause some breaks in the clouds by the afternoon as
has happened in previous days. Cloud cover forecast for Saturday may
be a bit on the optimistic side, but with the subsidence from the
high building in and somewhat drier air moving in from the northwest
think widespread breaks in the clouds are possible.
.LONG TERM...(Saturday night through Friday)
Issued at 320 PM CST Fri Dec 9 2016
The main focus in the extended is an area of low pressure moving
across the Central Plains late on Saturday northeastward into the
central Great Lakes by early Monday. This will bring accumulating
snowfall to the Northland. Despite only being 48-72 hours out, there
still are significant differences between forecast guidance. The
GFS/NAM are slower with a stronger system moving through, while the
ECMWF/CMC are faster with a broader low. Initially precipitation
will begin as a broad area of frontogenesis and isentropic lift
gradually spread snow northeastward late on Saturday. Snow will
continue through Sunday before coming to an end Sunday night into
Monday. The slower and stronger solutions extend an inverted trough
into the region, which in combination with a stronger trough aloft
brings more in the way of snowfall. The quicker and broader
ECWMF/CMC solutions bring less in the way of snowfall as the system
quickly skirts through. Still looking at snowfall amounts generally
between 2 to 4 inches from the Brainerd Lakes Region east to Park
Falls, which is closer to the GFS/NAM solution. Locations along the
North Shore of Lake Superior are likely to see lake effect
enhancement from easterly flow off the lake. If guidance continues
to trend towards the GFS/NAM solution, then headlines may be needed.
Held off on an advisory due to uncertainty.
Behind this system, a cutoff low will rotate southeastward from
northern Canada on Monday into Hudson Bay/Ontario by mid week. Will
see strong 850 hPa cold air advection beginning on Monday continuing
mid to late in the week. There is good agreement between the
GFS/ECMWF/CMC blasting arctic air into the Northland. Will see
periods of snow showers as the cutoff low rotates a series of
shortwaves into the region. In addition, due to northwesterly flow
will see periods of lake effect snow along the South Shore of Lake
Superior. Expect the coldest temperatures of the season mid to late
in the week with high temperatures in the single digits above and
below zero from Tuesday through Friday. Expect the coldest lows
Wednesday morning and Thursday morning with readings in the teens
below zero. Wind chills will be a concern with values in the 20`s to
30`s below zero from Tuesday morning to Thursday morning.
&&
.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1145 AM CST Fri Dec 9 2016
Cyclonic flow will continue across the Northland this afternoon
and tonight. This will combine with lift from a shortwave moving
southeastward from southern Manitoba to northern Lake Superior.
The result will be scattered snow showers this afternoon and
tonight. Expect ceilings to remain in the MVFR range between 1500
to 3000 feet for much of the forecast. In the heavier snow showers
expect visibilities to drop to MVFR/IFR range. More confident on
visibility reductions at KINL/KHIB per the latest observations
and the ARW/NMM/RAP.
Expect snow showers to come to an end at KDLH/KHIB/KBRD early
Saturday morning as high pressure nudges into the region. The
drier air advecting into the region aloft may be enough to scatter
skies out to VFR.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH -4 9 4 20 / 10 10 50 60
INL -8 7 -4 14 / 20 10 20 40
BRD -7 9 7 19 / 0 30 60 70
HYR 1 11 7 22 / 20 10 60 70
ASX 4 12 8 23 / 30 10 40 60
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
SHORT TERM...JJM
LONG TERM...WL
AVIATION...WL